What I’ve noticed, is that metal halide lights are WAY less common than HPS or mercury vapor offerings for city-owned streets. I was never sure why. Metal halide puts out a much better light quality than HPS. MH is my favorite HID source and I wish they became standard on streets rather than HPS. I’m not a fan of clear mercury either but I even like those better than HPS.

I get that they don’t last as long as MV or HPS, but they look good and they actually are a white light. MH NEMA heads and MH coach style lanterns or UFO style posr tops also seem rare. Now, LED has taken over, and quality LEDs have even better light quality than MH. HPS made visibly on roads worse, and they also were a very warm color which wasn’t the most appropriate for a street.

The only time you’d find an MH cobra or post top was in cities that refused to use HPS (like Charleston, SC) or in upscale parts of a city. MH NEMA heads are pretty much non-existent, and only Cooper made them.

Shoeboxes, floodlights, decorative teardrop lights, and acorns seem to be an exception, as they’re all common in MH. Wall packs, bay lights, grow lights, and recessed cans don’t count as they’re not street lights.

Because they have lower efficiency and frequently explode at EOL. Just imagine maintaining thousands upon thousands
of MH fixtures. You will need many more spare parts for all the shattered refractors and dented reflectors.

Conventional probe start MH, especially when operated horizontally in a cobrahead tended to perform pretty bad compared to MV or HPS in terms of lamp life. There were some horizontal probe start lamps developed with curved arc tubes but they required special lampholders to allow for the proper orientation so they weren't that common.  Pulse start and CMH was a bit better but by that time most cities already converted to HPS and only opted to use those systems for upscale areas with higher budgets.

Toronto used quite a bit of MH in the older parts, a lot of streets used MH gumball luminaires ranging from 70w to 150w replacing incandescent gumballs in the mid 90s. They tended to use dual arc tube pulse start quartz lamps to get better lamp life and the gumballs had vertical lamps which worked better than cobraheads. There were some cobraheads and decorative MH luminaires with horizontal lamps, but they weren't as common as the gumballs.